The present invention relates generally to turbocharged internal combustion engines and more specifically to an improved waste gate to be used in combination with a turbocharged internal combustion engine.
A common technique by which the output power from an internal combustion engine can be increased is the exhaust driven turbocharger. As economy becomes more important and smaller displacement engines are used, in order to provide more power when needed, turbocharges can be applied to an increasing number of vechicles. This is true for spark ignition engines as well as diesel engines. The diesel engine responds particularly well to turbocharging and up to now has been the largest user of turbochargers in trucks, tractors, heavy equipment and some automobiles.
A simple explanation of the function of a turbocharger showing the waste gate is illustrated in FIG. 1. The intake to the system is through a fuel control device 10, for example, a carburetor, to a compressor 12 of the turbocharger 14. The fuel/air mixture from compressor 12 is ducted to the intake valve 16 of cylinder 18 of the internal combustion engine. The exhaust from cylinder 18 exits exhaust valve 22 and drives turbine 24 of turbocharger 14 and is exhausted through exhaust 26. Connected in parallel with turbine 24 is waste valve 28, having inlet 30 and outlet 32. Control inlet 34 of waste gate 28 is connected between the output of compressor 12 and the intake valve 16 of cylinder 18.
The exhaust from the engine is passed through the turbine 24 which drives the compressor 12 which charges or pressurizes the combustion chamber of cylinder 18. In this manner, the volumetric displacement of the engine is effectively increased. The pressure applied to the engine intake is known as boost. The boost available is dependent on engine speed and load and must be regulated to some acceptable value. Since it is desirable to apply boost at low engine speed, the by-pass valve or waste gate 28 is utilized to reduce flow through the turbocharger at high engine speed or when sufficient boost is present.
The valve 28 must handle exhaust gases at temperatures from 1400 to 1700.degree. F. Waste gates or valves currently in use are mechanical, either spring loaded blow-off valves which are crude in their control of boost or diaphragm actuated valves which control boost more accurately. A typical example are U.S. Pat. Nos. 3,931,712 and 4,005,578. In either case these valves must be carefully made to handle the high temperature and vibrations present in the engine exhaust. This results in a valve which is very expensive and exhibits poor reliability due to the severe conditions in which it must operate. Failure of a waste gate can result in a damaged engine through burned pistons or destruction of the turbocharger itself due to overspeed.
Thus, there exists a need for a valve or waste gate to be used with a turbocharged engine having high reliability and longer life than those of the prior art. Although the system described in U.S. Pat. No. 3,931,712 suggests replacing mechanical pressure regulator 40 with a fluidic or electronic device, the output of the regulator is still used to drive hydraulic actuator 30 which controls a butterfly waste gate or by-pass valve 25. Thus, the total number of movable parts and elements which are capable of failure have not been optimized, even in the aforementioned U.S. patents.